Shot quality is a hot-button issue among people who spend time trying to learn about the game of hockey through statistical analysis.

Intuitively, we all know that shot quality exists. A quick blast from center ice immediately prior to a line change is far less likely to score than a superstar taking a shot on a breakaway. The question, then, isn’t whether shot quality exists – we know it does – but whether teams can use it to help them win games.

Defensive shot quality is hard to measure because of goaltending effects. If Boston posts a better save percentage this season than Columbus, we can’t say that it’s strictly a matter of their team playing better defense or a brilliant coaching stratagem – because Tim Thomas and Steve Mason are very different goaltenders. Various methods of measuring shot location to split defensive performance from goaltending performance remain problematic and unproven.

That problem, however, doesn’t exist when we look at team offense. A team’s shooting percentage tells us exactly how likely they were to score on any given shot. Therefore, if certain teams in the league are better than others at taking quality shots, it’s something that should show up when we look at their records from year-to-year.

Naturally, we’d want to level the playing field – some teams get more power plays or penalty kills, some teams spend more time in 4-on-4 situations, etc. To get a really even idea of what teams are good at taking quality shots, we’d only want to look at 5-on-5 game play – it’s the most common situation, the area where coaching and overall team ability should be most evident.

If we go back to 2010-11, the best team in the league at converting their shots was the Philadelphia Flyers. In 2009-10… they were the 27th-best team in the league. The Capitals were the best team in the league in 2009-10, and they fell all the way to 23rd in 2010-11. In fact, the average finish of a team that leads the league in shooting percentage in the previous and prior years is 14th overall in the NHL. Interestingly, the average finish of a team that finishes last in the league in shooting percentage in the previous and prior years is also 14th overall.

Still, those are just examples. To really see if shot quality matters offensively, we’d want to look at the entire league, over a period of years. Thanks to Behind the Net, we can do that – we have four years of 5-on-5 shooting data, from 2007-08 to 2010-11. We’ll run mathematical correlations, to see the relationship from one year to the next – a score of 1 represents a perfect correlation, a score of zero shows no correlation whatsoever.

2007-08 to 2008-09 correlation: 0.179

2008-09 to 2009-10 correlation: -0.067

2009-10 to 2010-11 correlation: -0.121

Average year-to-year correlation: -0.003

The average correlation is actually slightly negative over these years, but it’s very, very close to exactly zero. In other words, there seems to be no connection between how good a team’s shooting percentage is from one year to the next. This is a significant argument that there is no major difference between individual NHL teams in their ability to score on any given shot – over the big picture, shot quality in 5-on-5 situations evens out.

While a team’s shot quality seems to bounce around erratically from year to year, the same is not true of the number of shots that they take. Here are the same correlations, but this time instead of looking at team shooting percentage, we will look at team shooting rates (shots/60) in 5-on-5 situations:

2007-08 to 2008-09 correlation: 0.578

2008-09 to 2009-10 correlation: 0.453

2009-10 to 2010-11 correlation: 0.462

Average year-to-year correlation: 0.498

That’s not a perfect correlation by any means, but there’s clearly a relationship between how teams perform from one year to the next – something we didn’t find when we looked at shot quality.

Because shot rates are at least somewhat predictable, we can view them as a team skill – teams that are good at this one year stand a good chance at being good at it the next year. Because shooting percentage is unpredictable (at the team level) it becomes very difficult to argue that certain teams are better at it than others.

Jonathan Willis is a freelance writer.
He currently works for Oilers Nation, Sportsnet, the Edmonton Journal and Bleacher Report.
He's co-written three books and worked for myriad websites, including Grantland, ESPN, The Score, and Hockey Prospectus. He was previously the founder and managing editor of Copper & Blue.

Function operation: Press a key to show the normal time, and connect again out to insulate the slice.

1. Normal time mode: While opening the machine, the normal time shows to 12:0 Time establishes In the normal appearance, press “ÂƒÃº” the key enters 12 Hrs/ an appearance, press the key of SET into time, date establishes, and below the row order establishes respectively hour, minute, year, month, day etc., pass the UP/DOWN key match to complete its establish.

• Set up the scope: Year is 2000 – 2099, month is 1 – 12, day is 1 – 31, hour is 1 – 12 or 0 – 23, minute is 0 – 59.

• Establishes at the same time in the date, the week (from MON to SUN) the ground of cowgirl is automatic to change.

• At establish appearance, if have no a minute in key to then withdraws to establish automatically, combine the current in manifestation establishes a time, date, 12/24 mode conversion: In the normal appearance, press “ÂƒÃº” the key can enter a 12 Hrs/24 Hrs system conversion mode, passing the key of ÂƒÃ±ÂƒÃ² proceed the modification.

2. Alarm clock with love to sleep mode In the normal appearance, press “ÂƒÃº” key two or direct press “Âƒs” the key enters to make the bell mode. The alarm clock establishes In the alarm clock mode, press the key of SET in to make the bell establishes, and below the row order establishes respectively hour, minute, music, pass the ÂƒÃ±ÂƒÃ² key match to complete its establish. If open to make the bell only, but did not open love to sleep, then be to make the bell arrive enactment time, ring to make a minute. Keyed to stop arbitrarily ring make. If have opened love to sleep, then make every 3 minutes ring, every a minute, ring totally for 4 times.

• At love to sleep ring to make, keyed to stop ringing to make arbitrarily, but the love to sleep marking still gleams, keeping to 4 times ring make the be over or is canceled.

• At not love to sleep ring to make, press “ÂƒÃº” the key cancels this love to sleep function; (namely the marking stop the flicker) But press the key of ÂƒÃ± to then close the love to sleep marking.

• When make bell and love to sleep markings to open all and not, making the bell to close with love to sleeply at the same time. Only have at make the bell marking open, the love to sleep function just is valid.

3. The birthday reminds the mood. In the normal appearance, press “ÂƒÃº” the key can enter the birthday reminds the mode. The birthday reminds to establish. Remind the appearance in the birthday, press the key of SET into the date with establishes horaryly, pass the key of ÂƒÃ±ÂƒÃ² be matched with to complete its establishes, and below the row order establishes respectively:

• When time that birthday establishes when reminding arrives, broadcasting 5 minutes in song in birthday to bless birthday HAPPY!

• At establish appearance, if have no a minute in key to then withdraws to establish automatically, combine manifestation current a time, date for establishing.

4. Timer mode: In the normal appearance, press “Š” the key can enter the timer mode. The timer establishes. In the timer appearance, presses the key of SET in to establish, and below the row order establishes respectively hour, minute, pass the ‚ key match to complete its establish.

• Set up the scope: The hour is 0-23, minute 0-59.,

• The beginning accounts the hour: At position number that show the “DATA” from 00 change into 59 circulations are gradually decrease, current a minute for setting up the number gradually decrease open to start, the same a number for setting up gradually decrease also start.

• When account arrive 0:00:00 hours will ring to make to hint a minute, if front is in the appearance of TIMER, ringing to make at the same time to hold act last manifestation of 0:00:00 will gleam without intermission.

• At establish appearance, if have no a minute in key to then withdraws to establish automatically, combine the beginning accounts the hour.

5. Temperature mode Current environmental temperature in manifestation, in the normal appearance, the key of SET that press conversion proceeds Celsius /Fahrenheit.

6. Music listening mode In the normal appearance, pressing the key of ‚ can open or close the music. When the music opens, can circulate to broadcast 7 different pop musics.

The comments here remind me a lot of the evolution vs creationism debate. One side presents arguments, the other mock those arguments with no suggestion that they actually have the capacity to understand them. They laugh amongst themselves smug in the security of their ignorance.

Edit - There are certainly valid critiques of using stats and of any particular statistical arguments, however, there appear to be some individuals who mock any use of advanced stats or statistical analysis without ever showing any comprehension of them.

I thought the point was straight-forward: there seems to be no difference in shot quality between NHL teams. If there was, we'd see some teams perform well from year-to-year, and other teams perform badly. Instead, teams bounce around wildly.

Come on Jonathan, you use a historical picture and don't even give us a little insight? Thats one of the first times that the cup was used if I recall correctly. I cant remember what team that was, an amateur Montreal club, or Ottawa, it has escaped me. Beautiful piece of history if you ask me, although I can't quite put my finger on it...

Did they observe Movember back then? What's wrong with the sissies playing hockey these days...tiny stashes...concuss easily. These mustached men would kick the holy hell out of the "New Millennium Hockey Man." Is there a stat for that?

What about a scoring chance/shot on net ratio? Would that give you a better idea? You are talking about higher scoring chance but only mention shots and shooting percentage. Shots vs. scoring chances would paint a better picture I think. There should be a correlation there, teams that have a higher scoring chance ratio probably score more goals, me thinks.

You're assuming that a higher shooting percentage implies a higher shot quality. I would agree with this assumption if we recognize that shot quality is about more than just shot proximity, shot angle, and talent of the shooter. IMO, a quality shot also means you have a teammate at/near the front of the net screening the goalie and/or ready to bang in a rebound. That's why a lot of bangers and grinders have shooting percentages that are as high as finesse players.

I want to keep making the case for driving to the net and scoring more ugly goals. It really does work, but this practice still needs to be instilled in some players.

That's a pretty impressive piece of math/stats ~S~K, but for the life of me, I can't figure out what the hell all that means. Plus, anytime someone tells me that Toskala was a big winner during that year, despite playing poorly on two bad teams, I have to question if the data is of any value.

Function operation: Press a key to show the normal time, and connect again out to insulate the slice.

1. Normal time mode: While opening the machine, the normal time shows to 12:0 Time establishes In the normal appearance, press “ÂƒÃº” the key enters 12 Hrs/ an appearance, press the key of SET into time, date establishes, and below the row order establishes respectively hour, minute, year, month, day etc., pass the UP/DOWN key match to complete its establish.

• Set up the scope: Year is 2000 – 2099, month is 1 – 12, day is 1 – 31, hour is 1 – 12 or 0 – 23, minute is 0 – 59.

• Establishes at the same time in the date, the week (from MON to SUN) the ground of cowgirl is automatic to change.

• At establish appearance, if have no a minute in key to then withdraws to establish automatically, combine the current in manifestation establishes a time, date, 12/24 mode conversion: In the normal appearance, press “ÂƒÃº” the key can enter a 12 Hrs/24 Hrs system conversion mode, passing the key of ÂƒÃ±ÂƒÃ² proceed the modification.

2. Alarm clock with love to sleep mode In the normal appearance, press “ÂƒÃº” key two or direct press “Âƒs” the key enters to make the bell mode. The alarm clock establishes In the alarm clock mode, press the key of SET in to make the bell establishes, and below the row order establishes respectively hour, minute, music, pass the ÂƒÃ±ÂƒÃ² key match to complete its establish. If open to make the bell only, but did not open love to sleep, then be to make the bell arrive enactment time, ring to make a minute. Keyed to stop arbitrarily ring make. If have opened love to sleep, then make every 3 minutes ring, every a minute, ring totally for 4 times.

• At love to sleep ring to make, keyed to stop ringing to make arbitrarily, but the love to sleep marking still gleams, keeping to 4 times ring make the be over or is canceled.

• At not love to sleep ring to make, press “ÂƒÃº” the key cancels this love to sleep function; (namely the marking stop the flicker) But press the key of ÂƒÃ± to then close the love to sleep marking.

• When make bell and love to sleep markings to open all and not, making the bell to close with love to sleeply at the same time. Only have at make the bell marking open, the love to sleep function just is valid.

3. The birthday reminds the mood. In the normal appearance, press “ÂƒÃº” the key can enter the birthday reminds the mode. The birthday reminds to establish. Remind the appearance in the birthday, press the key of SET into the date with establishes horaryly, pass the key of ÂƒÃ±ÂƒÃ² be matched with to complete its establishes, and below the row order establishes respectively:

• When time that birthday establishes when reminding arrives, broadcasting 5 minutes in song in birthday to bless birthday HAPPY!

• At establish appearance, if have no a minute in key to then withdraws to establish automatically, combine manifestation current a time, date for establishing.

4. Timer mode: In the normal appearance, press “Š” the key can enter the timer mode. The timer establishes. In the timer appearance, presses the key of SET in to establish, and below the row order establishes respectively hour, minute, pass the ‚ key match to complete its establish.

• Set up the scope: The hour is 0-23, minute 0-59.,

• The beginning accounts the hour: At position number that show the “DATA” from 00 change into 59 circulations are gradually decrease, current a minute for setting up the number gradually decrease open to start, the same a number for setting up gradually decrease also start.

• When account arrive 0:00:00 hours will ring to make to hint a minute, if front is in the appearance of TIMER, ringing to make at the same time to hold act last manifestation of 0:00:00 will gleam without intermission.

• At establish appearance, if have no a minute in key to then withdraws to establish automatically, combine the beginning accounts the hour.

5. Temperature mode Current environmental temperature in manifestation, in the normal appearance, the key of SET that press conversion proceeds Celsius /Fahrenheit.

6. Music listening mode In the normal appearance, pressing the key of ‚ can open or close the music. When the music opens, can circulate to broadcast 7 different pop musics.

As informative as the article but DAMN!! my head hurts now, maybe it's to early for all this information.

Come on Jonathan, you use a historical picture and don't even give us a little insight? Thats one of the first times that the cup was used if I recall correctly. I cant remember what team that was, an amateur Montreal club, or Ottawa, it has escaped me. Beautiful piece of history if you ask me, although I can't quite put my finger on it...

Yeah, like why do they have the rabbit from Donnie Darko on the front of their sweaters? Something like that definitely has to affect shot quality.

So if you get a lot of shots then chances are eventually you will start scoring goals when your shooting percentage comes around. One problem with this thought is that it's ignoring what is causing that shooting percentage to turn around. Other problem is what if your percentage heads in a downward direction. :(

Take a look at the teams that are leading in shots right now they arent necessarily the same teams leading the league in points. I'd be willing to be that is true most every year.

I think this is one of those things were just using the simple stats to make any conclusion doesnt really tell you much. Sure it's probably a good thing to be outshooting other teams but it's not necessarily going to win you more games. For any real information from the stats I think you have to start breaking it down to more in depth stats like shot location. Where are all those shots coming from, where is your team giving up shots. I know it's a small sample size but the Canadiens game and the 2006 playoff run sure shows me that getting outshot doesnt necessarily mean you are getting outplayed.

I think the explanation is thus: a team could hypothetically win by taking higher quality shots, but there is a set range of areas from which a group of players will tend to shoot; therefore, any greater opportunity to take high percentage shots would also yield greater opportunity to take lower percentage shots and the ratio of shots:scoring chances would remain about equal. There's too much parity in the league for any given team to be notably above or below average in shooting percentage over an extended period (as a result of skill as opposed to luck).

There's also the possibility that any developments that would improve seasonal shooting percentage (e.g. the Stamkos PP one-timer) will be adapted to over time by opponents and thus variation in shooting percentage would regress. It's not really measurable so it doesn't matter from an analysis point of view, but it's a possible theory to account for some of the variation.

What Willis is saying here is that when evaluating a team and projecting them into the future, the best way to do that is to project them based on skill and not variance (read: luck). Skills are those things that are repeatable over time. Shot quantity is repeatable, there is a large correlation between a team's shot quantity from one season to the next. Shot quality is not repeatable, there is very little correlation from one season to the next. Thus, the truer skill, at the team level at least, is shot quantity. Obviously, shot quality has a massive impact on the outcome of games, and teams riding the shooting % bubble can do impressive things, but it is unsustainable over time. Conversely, the best teams since the lockout have been near the top of the shot quantity heap consistently, Det, SJ, Was.

Also, ~S~K~, DIGR has no more predictive value than ES SV%. It got some attention because it's a fancy stat, but because shot quality is hugely variable, season-over-season it shows no more correlation than a strictly shot quantity-based measure.

I think the Oilers either out-shot or sawed off with every team in that '06 Run once they got past the Red Wings. And I don't think anyone would argue that the real reason they got past Detroit was that Roloson played the best hockey of his life while Legace was vanilla -certainly the Red Wings controlled the play.

Any attempt to describe 'shot quality' by math must include shot distribution. This is a first step. This is the one value I see in DIGR.

To discuss shot quality without mentioning shot distribution would be like scientists announcing that they checked but could find absolutely no pictures in the newspaper, merely collections of variously shaded black and white dots.

There's too much parity in the league for any given team to be notably above or below average in shooting percentage over an extended period (as a result of skill as opposed to luck).

@Willis wrote:
"Exactly!"

Willis, count me as a stats novice interested in what I can learn from these new tools. That said, can I offer a humble suggestion?

Could you try to sum up your arguments with a bit more force. Victory gave me the essence of your article in a sentence. I appreciate the journey through the data you take me on... but sometimes find myself struggling to find the point you are trying to make. If you could be more direct in your conclusions it would help.

Did they observe Movember back then? What's wrong with the sissies playing hockey these days...tiny stashes...concuss easily. These mustached men would kick the holy hell out of the "New Millennium Hockey Man." Is there a stat for that?

These guys are definitely awesome and big props for the facial hair. It's a lost art. Just think there hasn't been a president to sport any since TR and Taft.

And, although I wager these guys were a scrappy bunch who possessed a sterner work ethic, I'd bet they would be dwarfed by today's NHL players in height, weight and muscle mass.

@ Willis; to get a more accurate picture you'd have to control for player changes, maybe by using aggregate players shooting percentages rather than straight-up team percentages.

Here's another question: any correlation between Shots For and wins? That would indicate if shot quantity even matters.

Bruce McCurdy with a long look at outshooting and wins etc at The Journal from last July: http://blogs.edmontonjournal.com/2011/07/18/paradigm-shift-the-evolving-relationship-between-outshooting-and-winning/

At the risk of showing my age, there was an old chestnut that the Soviets were the masters of the "don't shoot until you see the whites of their eyes" approach to offense. That is all shots were quality shots. I realize that stats keeping was not as detailed as it is today, but have you ever looked to see if the Soviets of the 70s did in fact only take "quality" shots? Example: The alleged "greatest game ever played" between Montreal Canadiens and Red Army on New Years Eve 1975 featured shots on goal of 35 to 13 respectively. So was Dryden's 0.769 save % an indication that the Soviets were very patient and precise or Dryden "sieved" out. Not making a point just curious.

Edit: took a quick look at the 72 Summit Series. Canada outshot USSR in 6 of 8 games but not by crazy margins. Interestingly the Godless Commies . . . . er . . . our Soviet friends, lost both games that they outshot Phil, Paul and the fellas. That is the extent of my statistical analysis.

1. Location fallacy: The assumption that location correlates directly with quality is specious.

It seems true in a 'linear' (FLOABTerm) sense, but it's false.

A shot from centre ice is lower 'quality' than a shot from the slot. Agreed

However, a "whacking, whacking, whacking" from the top of the crease is three low quality shots from in close vs a two-on-one Stamkos slapper from the top of the circles.

What about screened shots from the point vs shots from the same spot with no screen? Shot quality vs "play" quality is/was evident in "garbage" goals/crashing the net.

This is Location fallacy. (related: it's one of many reasons why we now coach goalies not to set their angle early, or too early. It's better to drive quickly to the angle and establish, than to glide out early toward the puck carrier as the play develops)

2. Playing to the score. The assumption that Team A consistently takes the same 'quality:skill' shots throughout the game is also specious.

I think the same conclusion with shot volume may be true about quality. When the score is tied or early in the game, the more 'skilled' team A will likely get higher quality chances than the 'unskilled' team B. Think of All-star games... or Canada vs Norway games.

Once the score is out of reach, Team A will likely be more inclined to make the safe shot, even if it's from in close, than the defenceman joining the rush 4 on 2 play. Returning to a position of protecting the lead and turning down the offence.

The "safe" shot is easier to save. Quality should spike and drop in correlation to playing to the score effects?

General concern: It's dangerous to say "We think we can subjectively see it, but mathematically, we can't find a strong correlation, therefore it probably doesn't exist and our subjective eye is being deceived."

I think the Oilers either out-shot or sawed off with every team in that '06 Run once they got past the Red Wings. And I don't think anyone would argue that the real reason they got past Detroit was that Roloson played the best hockey of his life while Legace was vanilla -certainly the Red Wings controlled the play.

You'd be wrong on the outshooting teams in 2006. They only outshot the Sharks in 2 of 6 games, they were out shot in all 5 games against the Ducks, in the finals the shot totals were very close and the Oil ended up losing.

The Bruins last year were outshot heavily in the playoffs, people say hot goalie but if that's the case hot goalies are fairly common. The link RB gave to the Mccurdy article is also very interesting.

It's clear that you can generally say that outshooting a team is probably a good thing but there is enough variation that you cant conclude that if your team is getting outshot they are necessarily playing bad.